Lehr drive for sheet glass machines



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p 1940. J. H. REDSHAW 2,215,231

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' Sapt. 17, 1940. J. H. REDSHAW LEHR DRIVE FOR SHEET GLASS MACHINE Filed Oct. 9, 1957 5 Sheets-Sheet 3 x/v VEN To R t/QSEPH H 95 UQ'HHW P 1940- J. H. REDSHAW 2,215,231

LEHR DRIVE FOR SHEET GLASS MACHINE Filed 001:. 9. 1937 5 Sheets-Sheet 4 INVENFOR. JASEPHH R's-as HA w A RNEYS.

w A H 5 D E R H I LEHR DRIVE FOR SHEET GLASS MACHINE Filed 001:. 9, 1937 5 Sheets-Sheet 5 Patented Sept. 17, 1940 UNITED STA'iEfi hATE.

'i" QFEECE 2,215,231 Luna DRIVE FOR snns'r GLASS MACHINES Vania Application October 9, 1937, Serial No. 168,237

2 Claims.

The invention relates to a lehr drive for sheet glass machines, such as those employed in the Fourcault and Slingluif processes involving the use of series of pairs of rolls in a vertical casing which grip the glass sheet between the members of each pair and provide the traction necessary for drawing the sheet continuously from a bath of molten glass in a forehearth. The rolls on one side of the sheet are ordinarily mounted in fixed bearings, while the rolls on the other side are carried in movable bearings pressed inward by weighted levers, thus providing yielding pressure between. each pair of rolls and permitting the drawing of glass sheets of varying thickness. The fixed rolls are ordinarily drivn directly from a vertical line shaft by the use of bevel gears, while the movable rolls are driven from the fixed rolls by suitable gears, often by, intermeshing spur gears on the adjacent ends of the fixed andmovable rolls. The drawing rolls are of asbestos composition subject to varying. amounts of wasting away, due to heat conditions, and depending on the location of the rolls in the lehr, the lower ones exposed to the greatest heat suffering the greatest reduction in diameter. As a result, the

peripheral speed of the rolls in different parts of the lehr varies in the course of time, so that slip page occurs between some of the rolls. and the glass sheet causing roll marks on the surface of the sheet.

One of the objects of the invention is to provide a drive which will obviate this difficulty and insure operation of all of the rolls at the, same peripheral speed, even though their relative diameters may vary due to the unequal wearing or wasting away of the roll surfaces.

A further object of the invention is to provide a drive which will give the drawing rolls on both sides of the sheet a smooth, uniform movement of rotation. In lehr drives, as heretofore constructed, the positive drive of the fixed driving rolls is smooth and uniform, but the drive of the movable rolls has been uneven due to the fact that their mounting for movement toward and from the fixed rolls has called for some lost motion in the gear devices. The present construction avoids this difficulty and further permits the rolls on both sides of the sheet to be mounted for movement without affecting the uniformity of rotation thereof.

Still another object of the invention is to prevent roll sag which occurs in the drawing of wide sheets. The diameter of the roll shaft is relatively small as compared with the diameter of the roll itself, and with long rolls, there is a substantial degree of sag intermediate the supporting end bearings,*which results in an uneven application of pressure on the glass sheet between the rolls. The present invention overcomes this difliculty and reduces any sag to a negligible degree.

A still further object is the regulation of the lehr temperature, by utilizing the metal driving rolls as coolers. These rolls are hollow and of relatively large diameter, so that the passage of cooling fluid, such as air, water, or steam therethrough may be made to serve as a temperature regulating means, the characterv and amount of the fluid being regulated in the various sections of the lehr so as to secure a properly graded temperature depending on requirements. One embodiment of the invention is illustrated in the accompanying drawings, wherein:

Figure 1 is a. fragmentary elevation, partly in section on the line" I-I of Fig. 2 of the lehr. a

Fig. 2' is a fragmentary side elevation partly in section on the line IIII of Fig. 4. Fig. 3 is a fragmentary elevation of the side of the lehr opposite to that of Fig, 1. Fig. 4 is a detail plan View showing a portion of the drive mechanism. Fig. 5 is a diagrammatic sectional view through a portion of the lehr. And Fig. 6 is a detailsectional view showing the means for circulating a cooling fluid through the drive rolls.

Referring to the drawings, "l, l are the side walls of the lehr casing, and i3, 8 are the end Walls thereof, a portion only of the lehr being shown. It will be understood that the glass sheet 9 is drawn from a. molten bath beneath the lehr in a continuous manner and that sections are cut off therefrom above the top of the lehr in accordance with established practice. Arranged in pairs along the length of the lehr are the drawing rolls l8, 3- and the driving rolls 1 i, ll, each drawing roll being supported upon a driving roll and driven therefrom, as later described. Each of the drawing rolls comprises a shaft l2 of steel or the like and a body portion made upof the discs I 3 of asbestos or other composition, which is relatively soft and subject to wear, material of this kind being employed to avoid marring the surfaces of the glass sheet. The roll shaft, i2 is supported at each end in the roller bearings M, M, and these roller bearings are carried on the ends of horizontal links l5, which links are pivoted at their outer ends to the short arms E6 of bell crank levers which are pivoted at the respective junctions of their arms l6 and H) to the wall of the casing at H and carry the weights IS on their horizontal arms I9.

so. I

Each end of each drawing roll is supported in this manner, and by regulating the position of the weight I8 on its arm, any desired pressure may be secured by the rolls l upon the glass sheet. The rolls, as thus mounted, are free to move independently in vertical directions, as well as to move horizontally toward each other and, in fact, constitute floating rolls, the entire weight of each of which is supported directly upon the driving roll H therebeneath. In order to provide for the positioning and removal of the rolls, the removable cover plates Ma (Fig. 2) are employed in the end walls 8 of the casing. In some cases, it is desirable to fix the position of the drawing rolls which lie to one side of the line of draw of the glass sheet and this result is accomplished by means of the stop bolts 20 (Fig. 3) which extend through brackets 2| carried by the casing of the lehr and engage the long arms IQ of the bell crank levers, thus limiting their downward movement.

The driving rolls ll upon which the drawing rolls rest are preferably of tubular form, as indicated in Fig. 2, and are supported in bearings 22 which are fixed to removable cover plates 22a secured to the end walls 8 of the lehr casing. These rolls are preferably of heat resisting metal, such as nickel chromium, and in practice, the wear upon the surfaces of these rolls incident to their contact with the drawing rolls is relatively slight, all the wear being taken by the asbestos surfaces of the drawing rolls. The diameter of the driving rolls is, therefore, maintained substantially constant, so that there is no variation in the speed of drive of the drawing rolls, as the drawing rolls have the same peripheral speed of rotation regardless of the amount which they may be worn away. The greater wear occurs in the lower levels of the lehr, where the heat action is more severe, but due to the arrangement as above described, this wear does not affect the uniform speed of rotation of the drawing rolls throughout the lehr, and as a consequence, no slippage of the rolls occurs with respect to the surfaces of the glass sheets such as would occur if such rolls in different parts of the lehr had different peripheral speeds.

If the driving rolls are nickel chromium, it is not necessary to provide cooling means to protect them. from the action of the heat in the lehr, but if such rolls are made of ordinary steel, it is desirable to provide a circulation of fluid therethrough to cool at least a number of them, as indicated in Fig. 6, wherein, the pipes 23 for carrying the fluid are connected to the ends of the rolls by means of the swivels 24. This protection of the rolls is particularly desirable in the lower sections of the lehr where the heat is greatest, and the amount of cooling may be regulated by the amount of fluid circulated through the rolls or by the character of the fluid; steam or air, for instance, having less cooling effect than water. When a cooling medium is employed in this manner in the driving rolls, it may be utilized as a temperature regulating means for the lehr. Uudue chilling in the lower sections of the lehr is not desirable, but after the glass has reached an elevation in the lehr where the temperature is above the critical annealing range, the use of fluid in the driving rolls, serves to reduce the temperature of the lehr rapidly, and so permits the lehr to be made shorter than would otherwise be the case.

The pairs of driving rolls are driven by means of the gearing shown in Figs. 2 and 4, wherein, 25 is an electric motor driving a horizontal countershaft 25 carrying worms 29 and 30, which engage worm wheels 3|, 3| on two vertical countershafts 2'1 and 28. The shaft 21 is provided with a worm 32 at the end of each pair of rolls H and such worm is engaged by a worm Wheel 33 on the end of the adjacent roll shaft. The other members of the pairs of rolls II are similarly driven from the vertical shaft 28 by means of worms on such shaft which engage worm wheels 34 on the ends of the roll shafts. The driving rolls II are thus all driven positively at the same speed, and this drive is communicated to the drawing rolls I0 by reason of the frictional contact due to the drawing roll resting freely upon the drive roll.

Fig. indicates diagrammatically a construction which may be employed in order to prevent slippage of any of the drawing rolls on the glass sheet due to the shrinkage of the sheet between the lower end of the lehr and the upper end thereof. Because of the temperature gradient from the bottom to the top of the lehr, ranging from about 1150 deg. F. at the lower end to about 200 deg. F. at the upper end, the length of glass lying between the two ends shortens to an appreciable extent, and if the drawin rolls were all driven at the same speed, a slight amount of slippage would occur between the roll surfaces and the glass sheet to compensate for this shrinkage. As indicated in Fig. 5, this compensation is secured by gradually decreasing the diameter of the drive rolls Ila from the lower pair of rolls upward, thus giving a corresponding decrease in the peripheral speed of the successive pairs of drawing rolls. This difference of diameter is exaggerated in the showing of Fig. 5, as in practice it would only amount to a few thousands of an inch between successive pairs of rolls. The slippage, without the use of the expedient, is relatively small, and in commercial machines heretofore, it has been disregarded. The present design permits the necessary correction to be made without recourse to a variation in the gear drives of the various pairs of drawing rolls which involves considerable mechanical difliculty and expense because of the small variations in speed to be provided for.

What I claim is:

1. In a vertical lehr for continuously drawing sheet glass from a molten bath of glass, substantially along a predetermined vertical plane of draw, said lehr including an upright supporting casing, a series of pairs of horizontally spaced relatively rigid and wear-resistant driving rolls having fixed bearings in the casing, the rolls of each pair being disposed upon opposite sides of the vertical plane of draw, a series of pairs of floating drawing rolls, in the casing, having relatively soft but heat-resistant surfaces subject to rapid wear in drawing sheet glass therebetween, gravity-actuated means urging the drawing rolls toward each other to effect contact with the surfaces of a sheet of glass being drawn, each drawing roll being substantialy completely supported upon and frictionally rotated by the surface of a driving roll and being free to move toward the driving roll to compensate for wearing away of the drawing roll surface, the axis of the driving roll being spaced from the plane of draw a substantially greater distance than the axis of the floating drawing roll when the latter is in contact with the sheet of glass being drawn, whereby the drawing roll tends to wedge between the driving roll and the sheet, in such manner that the pressure of the drawing roller upon the sheet and also upon the driving roll is proportional to the resistance of the sheet to the drawing action, and means for rotating the driving rolls.

2. A construction as defined in claim 1 in which the diameters of the driving rolls are pro-' gressiv-ely smaller from the bottom of the lehr upward, in order to drive the drawing rolls at progressively decreasing speeds to compensate for shrinkage in the length of the sheet of glass, 5 due to coolingas it ascends the lehr.

JOSEPH H. REDSI-IAW. 

